Removal from stainless steel surfaces of certain soils originating from an animal or vegetable source, such as charred animal or vegetable fats, fatty derivatives and other organic deposits from the cooking of food, has been a vexing problem in industries such as the food preparation industry, where essentially complete cleaning of such surfaces is desirable. In food service establishments, for example, stainless steel cooking surfaces may be found in food fryers which are heated to high temperatures for the cooking of large amounts of food. Soiling matter deposited on these surfaces may consist of a complex mixture of natural fats, fatty derivatives and other organic deposits from the cooking of food. During heating at high temperatures subsequent to deposition, this soiling matter may be converted into a charred, polymeric mass which is difficult to remove and which can comprise complex hydrocarbon chains containing fatty ester groups and ether linkages.
Such difficultly removable soils degrade shortening added for the frying of foods, reducing the useful life of added shortening and negatively affecting food quality and taste. Such soils also decrease the energy efficiency of the frying apparatus, which may become inefficient due to the thermal resistivity of the charred, carbonized buildup.
Removal of difficultly removable soils from food fryers has customarily been accomplished by a process known in the industry as a "boil-out," which typically involves adding an aqueous solution of a cleaner to a fryer, bringing the fryer to an elevated temperature, such as the boiling point of the cleaner, and maintaining the elevated temperature for a given period of time.
Effective removal of this type of soil is a considerable problem which in the past, even with a boil-out process, has required the use of highly corrosive, unsafe cleaners, typically based on highly alkaline caustics such as sodium or potassium hydroxide, sometimes accompanied by laborious scrubbing and/or scraping. The use of these products gives rise to serious hazards to the skin and eyes of the user. Such products may also damage adjacent surfaces, such as paint, aluminum or wood, with which they may inadvertently come into contact.
There has been a need in the industry to replace such dangerous, corrosive cleaners, with safer, noncorrosive products. A few noncorrosive products, such as trisodium phosphate, have been employed in boil-out processes. However, such noncorrosive cleaners have not proven to be adequate substitutes for the corrosive cleaners since, while safer, their cleaning effectiveness against difficultly removable soils is markedly lower.
Until now, therefore, those skilled in the art have been limited to selecting either relatively safe but ineffective cleaners or effective but hazardous cleaners.